1. Field of the Disclosure
The present invention relates generally image sensors. More specifically, examples of the present invention are related to image sensors with autofocus.
2. Background
Traditionally, autofocus is done in an inter-frame fashion. The lens of the image sensor moves throughout the autofocusing process. First, a first frame is obtained, and some property of that frame, e.g., contrast value, is obtained. Then, a second frame is obtained, and the same contrast value is obtained. The first and second contrast values are compared to see if the frame is coming into focus or going out of focus. Sharper contrast indicates coming into focus. The direction of the lens movement is adjusted accordingly. If the image is coming into focus, then the lens keeps moving in the same direction. If not, then the direction of the lens movement is reversed in the opposite direction.
The traditional inter-frame autofocusing method is relatively slow, because two image frames must be obtained in order to make a single comparison. The current invention solves this problem by obtaining certain property for comparison within a single frame. Here, autofocus is done in an intra-frame fashion.
Corresponding reference characters indicate corresponding components throughout the several views of the drawings. Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention.